Eh, more like OCD. I am always looking for new tweaks or .reg edits that will improve things. Keeping a clean OS by reinstalling Windows is a simple way to make sure that things are performing optimally.

In the "driver install" stage I like to install the video drivers last, because they enable some power saving features that generally aren't available till that point (like being able to kick the monitor into low energy mode, etc) and they need a system reboot anyway more often than not.